A cylinder lock is described and, more particularly, a cylinder lock comprising two or more independent locking mechanisms, including conventional tumblers and twisting tumblers and an associated locking bar. Also described is a key for operating the locking mechanisms when placed in a keyway of the cylinder lock.
Cylinder locks for locking doors, cabinets and other structures are well known in the art. Conventional cylinder locks typically include a cylinder shell, and a cylinder plug rotatably disposed within the shell. The interface between the interior surface of the cylinder shell and the exterior surface of the cylinder plug forms a shear surface. A plurality of tumbler pins are reciprocally mounted in chambers extending through the shell and the plug. The tumbler pins are a series of spring-driven segmented pins, including an upper portion and a lower portion. The cylinder lock is in a locked condition when the upper portions of the tumbler pins project across the shear surface preventing the cylinder plug from rotating relative to the cylinder shell.
The cylinder plug has a longitudinal slot or keyway for receiving a key blade of a key. Notches of varying depth along the top of the key blade define a key code for the cylinder lock. A properly configured key blade displaces the tumbler pins to a position where a joint between the upper portion and the lower portion of each pin is aligned with the shear surface. In this position, the cylinder lock is in an unlocked condition, which permits rotation of the cylinder plug relative to the cylinder shell. One portion of each tumbler pin rotates with the plug and the remaining portions of the tumbler pins are stationary within the shell. The cylinder plug is typically coupled with a lock actuator that rotates with the plug for releasing a securing mechanism, such as a dead bolt, upon rotation of the plug.
A second independent locking mechanism can also be provided in the form of a second set of tumbler pins. The second set of tumbler pins may be operated by a corresponding lock code cut in the form of notches of varying depth or angle along the sides of the key blade. The second set of tumbler pins can control a secondary locking structure, including a locking bar positioned in the cylinder plug. The locking bar rests in a camming slot of the cylinder shell preventing relative rotation of the cylinder plug and cylinder shell. When the second set of tumblers are received in corresponding notches of the key blade, the tumblers are displaced transversely permitting rotation of the cylinder plug by a camming action on the locking bar.
A problem with cylinder locks is the spring-driven tumbler pins, which typically comprise small coil springs. As a result, cylinder locks are not fully reliable since the springs may become weaker over time or be damaged as a result of environmental variations.
For the foregoing reasons, there is a need for a cylinder lock with two or more locking mechanisms and a complementary key. The new cylinder lock should provide an improved biasing element that overcomes the problems associated with the use of coil springs.